Conventionally, polyesters or polyethers containing hydroxyl groups at the ends of the molecules have been mainly used as soft segments of polyurethanes such as thermoplastic elastomers.
Among them, polyesters represented by adipates are poor in hydrolysis resistance so that polyurethanes obtained by using them, for example, are susceptible to cracks or molds on the surfaces in a relatively short time and therefore, they are limited in their use. On the other hand, polyurethanes obtained by using polyethers have good hydrolysis resistance, but they are disadvantageously poor in weather resistance and heat resistance (especially heat aging resistance). Further, polyester-based thermoplastic elastomers and the like also had similar problems to those with the polyurethanes because of recent demanding requirements for heat resistance (especially heat aging resistance), weather resistance, hydrolysis resistance, mold resistance, oil resistance and the like.
To solve these problems, polycarbonates containing hydroxyl groups at the ends of the molecules are used as soft segments especially in applications requiring high physical properties such as hydrolysis resistance, weather resistance, heat resistance (especially heat aging resistance) and the like because carbonate bonds in their polymer chain are very stable (non-patent document 1).
On the other hand, patent document 1 discloses polycarbonate diols represented by formula (1) below, characterized in that they have a terminal primary OH content of 95 to 98.5%.

Further, patent document 2 discloses polycarbonate diol-containing compositions comprising a polycarbonate diol having a number average molecular weight of 250 or more and 5000 or less and a hydroxyl group content of 95 mol % or more relative to all terminal groups, a phosphorus compound, and a hindered phenol compound.